Information recording member

ABSTRACT

In a data recording member having a data recording film which is formed on a substrate either directly or via at least one of inorganic and organic protective layers and which causes the change of atomic arrangement upon being irradiated by recording beam, the improvement wherein said data recording film has an average composition in a direction of the film thickness expressed by the following formulas: 
     
         M.sub.x Te.sub.y Se.sub.z O.sub.α 
    
     wherein x, y, z and α are values within the ranges of 2≦x≦40, 30≦y≦95, 3≦z≦45, 0≦α≦20, and M is at least one element selected from the group consisting of As, Sb, Bi, S, Si, Ge, Sn, Pb, Al, Ga, In, Tl, Zn, Cd, Au, Ag, Cu, Ni, Pd, Rh, Cr, Mo, W and Ta.

This is a division of application Ser. No. 642,260, field Aug. 20, 1984,now U.S. Pat. No. 4,637,976.

BACKGROUND OF THE INVENTION

This invention relates to an information recording member which makes itpossible to record on a real time basis frequency-modulated analogsignals such as video and audio signals or digital data such as computerdata, facsimile signals, digital audio signals, and the like, on aninformation recording film formed on a predetermined substrate, using arecording beam such as laser light.

Various principles exist for recording information on a film using laserlight. Among them, information recording based upon the change of atomicarrangement such as the phase transition (or phase change) of a filmmaterial, photodarkening, and the like, has the advantage that two discscan be directly bonded to form a two surface disc because deformation ofthe film hardly occurs. Moreover, rewrite of the information can also bemade by selecting a suitable composition. A large number of inventionsrelating to the recording of this kind are known, and the earliest ofall is disclosed in U.S. Pat. No. 3,530,441. This prior art referencediscloses a large number of films such as a Te-Ge film, an As-Te-Gefilm, a Te-O film, and so forth. Japanese Patent Laid-Open No.28530/1980 discloses Te-O-Se and Te-O-S films. However, it is extremelydifficult to produce the films using these materials, and stabilityunder the amorphous state is not sufficiently high.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide animproved information (data) recording member.

It is another object of the present invention to provide a datarecording member which has high reproducibility in the productionprocess thereof and which remains stable for an extended period of time.

In an information recording member having an information recording filmwhich is formed on a substrate either directly or via at least one of aninorganic protective layer and an organic protective layer and whichcauses the charge of atomic arrangement upon irradiation of recordingbeam, the objects of the present invention described above can beaccomplished by an information recording member characterized in thatthe information recording film has an average composition, in adirection of the film thickness (i.e., perpendicular to the surface)expressed by the following formula:

    M.sub.x Te.sub.y Se.sub.z O.sub.α

wherein x, y, z and α are values within the ranges of 2≦x≦40, 30≦y≦95,3≦z≦45 and 0≦α≦20, and M is at least one element selected from the groupconsisting of As, Sb, Bi, S, Si, Ge, Sn, Pb, Al, Ga, In, Tl, Zn, Cd, Au,Ag, Cu, Ni, Pd, Rh, Cr, Mo, W and Ta.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the internal structure of a vacuumevaporator used for producing a data recording member of the presentinvention; and

FIGS. 2 and 3 are sectional views showing the structure of the datarecording members in the embodiments of the present invention,respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Among the elements represented or expressed by M, at least one of Sn andIn are preferred and of these, Sn is particularly preferred because itenhances the stability under the amorphous state. However, the film canbe formed more easily in In than Sn. Sb is the next preferable element.The element which provides this effect when used in combination with atleast one of Sn, In and Sb is at least one element selected from thegroup consisting of Ge, Si, Bi, S, Pb, Al, Zn, Cd, As, Au, Ag, Cu, Niand Pd. Among them, one of Bi and Pb is particularly preferable.

In the data recording film of the present invention, theoxygen-containing film is preferably produced by first forming a filmwhich does not contain oxygen and is expressed by the formula M_(x)Te_(y) Se_(z), and then heat-treating this film in air of high humidityor radiating ultraviolet rays to the film. In this case, the film isoxidized at least near its surface, and oxygen comes into the film attimes. Accordingly, the average composition of the film in the directionof its thickness is expressed by the general formula M_(x) Te_(y) Se_(z)O.sub.α, where α is not zero (0) but is a value below 20. If oxygen isintroduced by such a method, the composition can be controlled moreeasily than by evaporation of oxide or by sputtering.

The properties can be improved in many cases if at least two elementsrepresented by M co-exist. Examples of the combination that can be usedinclude In and Sb, Sn and Ge, Pb and Sn, Sn and Bi, Sn and S, In and Pb,In and Bi, Sb and Bi, Sb and S, Sb and Pb, Sb and Sn, Sb and Ge, As andSn, and As and Sb. Among them, the combinations of Sn with otherelements are preferable.

The distribution, in the direction of film thickness, of the content ofthe element expressed by M may be arbitrary, but it is preferred thatthe content increases at either one of the surface portions (which mightbe an interface with other layers at times) of the recording film thanthe inside of the film, because spontaneous crystallization from nearthe film surface at which nuclei of micro-crystals are likely todevelop, can be prevented. For the same reason as described above, thedistribution in the direction of film thickness, of the content of Semay be arbitrary, but the content preferably increases near the surface(interface). Incidentally, the film may contain trace amounts ofelements other than those expressed by M.

The films, which hardly contain oxygen, can be easily formed, have highcrystallization temperatures and provide high stability.

Preferably, at least one of the surfaces of the recording film of thepresent invention is protected by another material which is in closecontact with that surface. The protective layer may consist of anacrylic resin sheet or a polycarbonate resin sheet which is thesubstrate, or at least one of organic materials such as ultravioletlight cured resins, epoxy resins, acrylic resins, polyester resins, orthe like. The protective layer may also consist of at least one ofinorganic materials, such as oxides, sulfides, fluorides, carbides,nitrides, or carbon. The substrate which consists of glass, quartz orsapphire, can serve as one of the inorganic protective layers. From theaspect of heat resistance, the surface of the recording film ispreferably in close contact with the inorganic material. However, if thethickness of the inorganic layer is increased, crack and drop oftransmissivity and sensitivity are likely to occur. It is, therefore,preferable that a thick organic layer is disposed in close contact withthe inorganic layer on the opposite side to the recording film. Theorganic layer may be the substrate, and in such a case, deformation ofthe recording film becomes difficult to occur. Examples of the organicmaterials are polystyrene resins, acrylic resins, polycarbonate resins,epoxy resins, ethylene-vinyl acetate copolymers known as hot meltadhesives, binders, and the like. Ultraviolet-cured resins may also beused.

The protective layers consisting of the inorganic materials can beformed in their final compositions, but can be formed more easily byfirst forming a film made of at least one member selected from the groupconsisting of a metal, a semi-metal or a semiconductor, and then makingthe film react with at least one of O, S and N. Examples of theinorganic protective layer include those whose principal or majorcomponents have the composition analogous to CeO₂, La₂ O₃, SiO, SiO₂,In₂ O₃, Al₂ O₃, GeO, GeO₂, PbO, SnO, SnO₂, Bi₂ O₃, TeO₂, WO₂, WO₃, CdS,ZnS, CdSe, ZnSe, In₂ S₃, In₂ Se₃, Sb₂ S₃, Sb₂ Se₃, Ga₂ Se₃, MgF₂, CeF₂,GeS, GeSe, GeSe₂, SnS, SnSe, PbS, PbSe, Bi₂ Se₃, Bi₂ S₃, TaN and C.

Among them, the compositions comprising GeO₂ or Al₂ O₃ are preferablebecause vacuum evaporation is easy, surface reflectivity is not muchhigh and the film is stable. Next preferred are compositions whichconsist essentially of SiO₂. It will be appreciated that GeO₂ and Al₂ O₃formed by vacuum evaporation are nonstoichiometric materials. Whenrecording is effected by means of the phase transition, it is preferredthat the entire surface of the recording film be crystallized inadvance. When the organic material is used for the substrate, however,the substrate can not be heated to a high temperature, so that the filmsurface must be crystallized by other methods. In such a case, thecombination of ultraviolet light radiation with heating, radiation ofthe light from a flash lamp, or the like, is preferably conducted.Crystallization may be generated only on the recording track with thespacings between the tracks kept amorphous. It is, of course, possibleto make recording on a recording film under the amorphous state bycrystallization.

Generally, in the case of recording films which make recording by meansof the change of atomic arrangement such as the phase transition, theread signal intensity or the degree of modulation can be improved if alight reflection (absorption) layer is disposed close to the recordingfilm. If data rewriting is effected a large number of times or ifrecording is made using a beam having excessively high power, however,mutual diffusion and reaction will occur between the recording film andthe light reflection layer. For this reason, it is preferred to disposean intermediate layer consisting of at least one stable member selectedfrom the group consisting of an oxide, a sulfide, a fluoride or anitride between the light reflection layer and the recording film. Themelting point and boiling (sublimation) point of this layer arepreferably higher than at least the melting point of the recording film.Where the light absorption by the recording film is less, the lightreflection layer absorbs the light and the resulting heat is transmittedto the recording film so as to make recording, the intermediate layerdescribed above is preferably up to 100 nm (0.1 μm) thick, andparticularly preferably from 1 nm to 50 nm thick, in order to improvethe heat transfer efficiency. The inorganic materials such as GeO₂, Al₂O₃, and the like that can be used as the protective layer, can all beused as the intermediate layer.

The preferred ranges of thickness of the layers described above aretabulated below:

recording film: 3 nm to 300 nm

inorganic protective layer: 1 nm to 5 μm (0.1 to 20 mm when protectionis made by the inorganic substrate itself)

organic protective layer: 10 nm to 10 mm

light reflection layer: 5 nm to 300 nm

Each of the layers described above can be formed by selecting a suitablemethod from vacuum evaporation, evaporation inside gas, sputtering, ionbeam evaporation, ion plating, electron beam evaporation, injectionmolding, casting, spin coating, and plasma polymerization.

The recording member in accordance with the present invention can beused not only in the disc form, but also in tape or other forms.

Hereinafter, the present invention will be described in further detailwith reference to examples thereof.

EXAMPLE 1

A tracking groove replica was formed on the surface of a disc-like,chemically reinforced glass sheet having a diameter of 30 cm and athickness of 1.2 mm using an ultraviolet-cured resin and celluloseacetate, and one track was divided into 64 sectors with the start ofeach sector having an engraved sector address, thereby providing asubstrate 14. The substrate 14 was then disposed inside a vacuumevaporator having an internal construction such as shown in FIG. 1. Fourevaporation boats 1 through 4 were arranged inside the evaporator. Theseboats were positioned on the circumference concentric with the centershaft 5 of the revolution of the substrate below the portions of thesubstrate at which data were to be recorded. Te, Se, Sn and GeO₂ wereplaced into these boats, respectively. Masks 6 through 9 each having afan-like slit and shutters 10 through 13 were interposed between theboats and the substrate, respectively. While the substrate was beingrotated at 120 rpm, a current was caused to flow through each boat toevaporate the material inside the boat.

The evaporation quantities from the boats were detected by quartzcrystal oscillator-type thickness monitors 15, 16, 17 and 18,respectively, and the current caused to flow through each boat wascontrolled so that the evaporation rate became constant.

As shown in FIG. 2, an about 80 nm-thick protective layer 20 having acomposition comprised of GeO₂ was first formed on the substrate 19.Next, a recording film 21 having a composition consisting essentially ofSn₁₀ Te₆₅ Se₂₅ was evaporated in a thickness of about 50 nm. Aprotective layer 22 having a composition comprised of GeO₂ was againevaporated in a thickness of about 80 nm. Likewise, a protective layer20' having a composition comprised of GeO₂, a recording film 21' havinga composition consisting essentially of Sn₁₀ Te₆₅ Se₂₅ and a protectivelayer 22' having a composition comprised of GeO₂ were evaporated onanother substrate 19' of the same size and material. Polystyrene layers23 and 23' were then coated in a thickness of about 0.5 μm on theevaporation films of the resulting two substrates 19 and 19',respectively, and both substrates were bounded by an organic adhesivelayer 24 with the polystyrene layers facing inward with each other,thereby forming a disc.

The light from a flash lamp was repeatedly radiated to the disc fromboth surfaces so as to sufficiently crystallize the Sn₁₀ Te₆₅ Se₂₅recording films 21 and 21'. Recording was made in the following manner.While the disc was being rotated at 1,800 rpm, the light from asemiconductor laser (wavelength: 820 nm) was kept at a level at whichrecording was not made, was converged by a lens inside a recording headand was radiated to one of the recording films through the substrate.The head was driven by detecting the reflected light in such a fashionthat the center of the groove for tracking was always in agreement withthe center of the light spot. While tracking was thus conducted,automatic focusing was established so that the focus existed on therecording film, and recording was made by increasing or returning to theoriginal level the laser power in accordance with the data signals. Jumprecording to another groove was also made, whenever necessary. In thecourse of recording, the change of reflectivity, which presumablyresulted from the change of the film to the amorphous state, occurred onthe recording film. In this recording film, the recorded content couldbe erased by radiating laser light whose length in the track directionwas greater than that of the recording light spot and whose length inthe direction to the adjacent tracks was close to that of the recordinglight spot.

If the distance between most adjacent pits, that represents the address,was from 1/2 to up to 2 times the length of the erasing light spot inthe track direction track and sector address can be read also by theerasing light spot, and the pit length representing the address ispreferably at least 1/2 times the length of the erasing light spot inthe track direction. This also held true of the other pits disposed at aheader portion.

Read of data was conducted in the following manner. While the disc wasbeing rotated at 1,800 rpm and tracking as well as automatic focusingwere being effected in the same way as in the recording mode, theintensity of the reflected light was detected by such laser power thandid not generate recording and erasing, thereby reproducing the data.This embodiment provided an error rate of about 1×16⁻⁶. In the course oflife test at 60° C. and a humidity of 95% for 6 months, the error rateincreased to 2×10⁻⁶, but this rendered no problem in practice.

When the composition was changed in the Sn_(x) Te_(y) Se_(z) recordingfilm, the error rate after life test at 60° C. and a relative humidityof 95% for 6 months was as follows. Here, x representing the atomicpercent of Sn was 10 (x=10), z representing the atomic percent wasvaried with the following results of Se:

    z=0:˜5×10.sup.-5,

    z=5:˜2×10.sup.-6,

    z=45:˜1×10.sup.-5,

    z=3:˜1×10.sup.-5

    z=35:˜2×10.sup.-6

    z=60:˜5×10.sup.-5

The error rate became greater with the smaller z value because ofoxidation, while the error rate became greater with the greater z valuebecause of crystallization of the recorded points or pits.

When x was changed with z being kept at a constant value 25, the changefrom the crystal state to the amorphous state became difficult when xexceeded 40. When x was below 2, the error rate did not reach the orderof 10⁻⁶ because the crystal size was great and noise occurred. Moreover,the stability under the amorphous state was low. When x was greater than5, the error rate was below 2×10⁻⁶. Within the range in which x was notmore than 25 and z was not more than 35, crystallization temperaturebecame high and stability was improved if either one, or both, of x andz became great.

The Sn-Te-Se system recording film must be at least 3 nm thick in orderto obtain sufficient stability and necessary contrast for data reading.Unless the film is below 300 nm thick, the sensitivity will drop due toheat conduction. Therefore, a preferred range of thickness is from 30 nmto 150 nm. The GeO₂ protective layer must be at least 1 nm thick inorder to obtain its effect, but is preferably up to 5 μm thick in orderto prevent the occurrence of cracks, and the like. If the thickness isfrom 20 nm to 200 nm, the film can withstand the storage under a severeconditions. The organic layer outside the GeO₂ layer must be at least 10nm thick in order to exhibit its effect, and particularly preferably, atleast 10 m thick. Moreover, it must be up to 10 mm thick so that thelight can be converged by the lens. If the Al₂ O₃ layer is used in placeof the GeO₂ layer, the film formation becomes difficult, but a highprotective effect can be obtained when rewriting the data. Nextpreferred is the SiO₂ layer.

The oxidation resistance of the Sn-Te-Se system recording film can beincreased and its crystallization during storage can be prevented byforming a region, in which the content of at least one of Sn and Se isincreased, at least one of the portions near the interface between thefilm and the protective layer having a composition comprising GeO₂ onthe substrate side and the portion near the interface between the filmand the protective layer having a composition comprising GeO₂ on theside opposite to the substrate, by changing the open angle of eachshutter during vacuum evaporation of the film.

At least one member selected from the group consisting of In, As, Bi, S,Si, Ge, Pb, Al, Ga, Sb, Tl, Zn, Cd, Au, Ag, Cu, Ni, Pd, Rh, Cr, Mo, Wand Ta may be added in place of part of Sn or substituted for all of Sn,and the amount of addition of such a member is substantially the same asthat of Sn. However, merits and demerits exist in accordance with theselected element. In the case of Ge and Si, for example, it is difficultto carry out deposition by vacuum evaporation with highreproductibility. In the case of As, deposition by vacuum evaporationwith high reproducibility is also difficult and in addition, toxicity ishigh and dust is likely to be produced during vacuum evaporation. Thestability is low for addition of Bi in the amorphous state. In, Ga, Tl,Zn, Cd, Pb and As are easily oxidizable. Vacuum evaporation of S isdifficult. Sb provides high toxicity when oxidized. Au and other metalelements involve the problem that they increase the heat transfercoefficient and reduce the sensitivity. However, In, Sb, As, Ge and Sihelp stabilize the amorphous state. The advantage of In over Sn is thatvacuum deposition is easier. In and Sb may replace the full amount of Snkeeping the high performance of the recording film.

It is possible to use, in place of at least one of the GeO₂ protectivelayers, a layer whose principal or major component is at least onemember selected from the group consisting of CeO₂, La₂ O₃, SiO, In₂ O₃,Al₂ O₃, GeO, GeO₂, PbO, SnO, SnO₂, TeO₂, WO₂, WO₃, CdS, ZnS, CdSe, ZnSe,In₂ S₃, In₂ Se₃, Sb₂ S₃, Sb₂ Se₃, Ga₂ S₃, Ga₂ Se₃, MgF₂, CeF₃, GaF₂,GeS, GeSe, GeSe₂, SnS, SnSe, PbS, PbSe, Bi₂ Se₃, Bi₂ S₃, TaN and C,besides Al₂ O₃ and SiO₂ heretofore described. However, if an opaquelayer consisting of carbon or the like is disposed on the light incidentside, the film thickness must be reduced. It will be appreciated thatwith a disc-shape substrate having a diameter of 30 cm, a recording filmwill have a radius in a range of from 6 to 14.5 cm and the radius of theprotective layer or film is the same or larger than that of thesecondary film. The radius of a polystyrene layer is the same or largerthan that of the protective layer.

EXAMPLE 2

The substrate used was an acrylic resin sheet having on the surfacethereof a groove for tracking formed by injection molding. A GeO₂ filmand a recording film were deposited by vacuum deposition on thesubstrate in the same way as in Example 1. After an about 80 nm thickSn₁₀ Te₆₅ Se₂₅ recording film was formed, the substrate was once takenout from the vacuum chamber, and ultraviolet rays were irradiated at 25°C. and a humidity of 80% to oxidize the film. Oxidation took place morevigorously, of course, at the surface, at which the contents of Sn andSe decreased. However, the interior part of the film was also oxidized,and the average composition in the direction of film thickness wassubstantially Sn₉ Te₅₉ Se₂₂ O₁₀. Te of the surface was oxidized and theTe ions at portions close to the surface moved to the surface and wereoxidized. At the under part of the surface, Se and Sn were retained.Subsequently, the substrate was again placed into the vacuum evaporator,and an about 80 nm thick film having a composition comprising GeO₂ wasdeposited by vacuum evaporation on the recording film. Similarly,another substrate was produced, and an about 0.5 μm thick acrylic resinwas coated on each evaporation film having a composition comprisingGeO₂. Thereafter, both substrates were bonded to each other by anorganic adhesive with the acrylic resin layers facing inward with eachother, thereby forming a disc.

The methods of crystallization, recording, erasing and reading weresubstantially the same as those of Example 1.

Introduction of oxygen into the recording film may be effected by usingTe oxide in place of Te as the evaporation source, but reproductibilityof vacuum evaporation is low and control becomes difficult.

When the average composition of the recording film is expressed by thegeneral formula Sn_(x) Te_(y) Se_(z) O.sub.α, the preferred ranges of xand z are substantially the same as those of Example 1. However,experiments were carried out while keeping α fixed at about 10. Thepreferred range of α is up to 20 atomic %, and if α is from 20 to 35atomic %, wrinkles and cracks, which might result from the increase inthe internal stress of the film, are more likely to occur. However, therecording, reproducing and erasing characteristics remain at usablelevels. If the oxygen content exceeds 35 atomic %, the sensitivity dropsremarkably.

At least one of the other elements such as Sb can be added in place of apart of or all of Sn, and the Al₂ O₃ layer can be used in place of theGeO₂ layer, in the same way as in Example 1.

The preferred thickness of each film is the same as that of Example 1.

The recording member obtained by this example had long life in the sameway as that of Example 1.

EXAMPLE 3

A GeO₂ layer 26 and an about 40 nm-thick Sn₁₀ Te₆₅ Se₂₅ film 26 wereformed on a substrate 25 similar to the substrate of Example 2, in thesame way as in Example 2 as shown in FIG. 3. After these films wereoxidized to an Sn-Te-Se-O film 27, a GeO₂ film 28 was about 10 nm thick,and an about 30 nm thick layer 29 having a composition close to Bi₂ Te₃was formed on the film 28. Furthermore, an about 80 nm-thick GeO₂ layer30 was deposited by vacuum deposition on the layer 29. Film formationuntil this stage was conducted by vacuum evaporation. One othersubstrate was formed in the same way as described above. After about 50μm-thick ultraviolet light cured resin layers 31, 31' were coated on theuppermost GeO₂ layers 30, 30' of both substrates, respectively, bothsubstrates were bonded to each other using a pressure sensitive adhesive32 with the UV-cured resin layers facing inward with each other, therebyforming a disc.

The methods of crystallization, recording, erasing and reading weresubstantially the same as those of Example 1. In the recording film ofthis example, the Sn and Se contents dropped near the interface of thefilm with the GeO₂ layer due to selective oxidation of Te.

In this example, light absorption by the Sn-Te-Se-O layer is less, sothat the recording light are greatly absorbed by the Bi₂ Te₃ layer, andthe resulting heat is transmitted to the Sn-Te-Se-O film. Theintermediate GeO₂ layer between the Sn-Te-Se-O film and the Bi₂ Te₃layer was disposed in order to prevent their mutual diffusion when writeand read of data are repeatedly made. Therefore, if this layer isexcessively thick, the heat transfer efficiency from the Bi₂ Te₃ layerto the Sn-Te-Se-O film, and hence recording sensitivity, will drop.

In order to obtain practical recording sensitivity, the GeO₂ layer ispreferably up to 50 nm thick. This also holds true when Al₂ O₃, SiO₂ orother transparent material is used in place of this layer. It is alsopossible to use a layer whose principal component is CeO₂ or the like,in place of GeO₂ layer in the same way as in Example 1. In this example,it is further possible to use a film, in which absorption of thesemiconductor laser light hardly occurs, but recording by means of phasetransition is possible, such as a film consisting of Sb₂ Se₃ as theprincipal component, in place of the Sn-Te-Se-O film. It is naturallypossible to use those Sn-Te-Se-O or Sn-Te-Se films whose Sn issubstituted by at least one other element such as In, or a recordingfilm whose principal component is a Ge-Te-Se system material, in thesame way as in Example 1.

In order to exhibit the light reflection and light absorption effects,the Bi₂ Te₃ layer must be at least 5 nm thick. It must be up to 300 nmin order to reduce the drop of sensitivity due to heat conduction. Thepreferred thickness of the other layers is the same as that of Example1.

A variety of semiconductors, semi-metals, metals, and their mixtures andcompounds such as Bi, Te, Sn, Sb, Al, Au, Pd, and the like, can be usedin place of Bi₂ Te₃.

EXAMPLE 4

An about 4 μm-thick polystyrene layer was formed by spin coating on analuminum alloy disc having a diameter of about 35.5 cm. Next, alaminated film of GeO₂ /Sn₁₀ Te₆₅ Se₂₅ /GeO₂ was formed on thepolystyrene layer in the same way as in Example 1, and an about 200μm-thick fluorocarbon plasma polymerized film was further formed on thelaminated film. In this disc, the light for recording, reproduction anderasing was incident from the side opposite to the aluminum alloy sheet.

The preferred range of the content of each element is the same as thatof Example 1. A part or all of Sn may be substituted by at least oneother element such as In, and CeO₂, or the like, may be used in place ofGeO₂, in the same way as in Example 1. A reflection layer such asdescribed in Example 3 may be interposed between the GeO₂ layer on thesubstrate side and the Sn-Te-Se film. In this case, it is morepreferable to dispose an intermediate layer such as described in Example3 between the reflection layer and the recording layer.

The preferred thickness of each layer is the same as that of Example 1.

As described above, the present invention can provide a recording memberhaving high reproducibility and high stability for an extended period oftime by a simple production process. Rewrite of data can also be made.

What is claimed:
 1. A method of recording and reproducing informationcomprising the steps of: (1) providing an information recording filmhaving an average composition, in a direction of the film thickness,expressed by the following formula:

    M.sub.x Te.sub.y Se.sub.z O.sub.α

wherein x, y, z and α are values within the ranges of 2≦x≦40, 30≦y≦95,3≦z≦45 and 0≦α≦20, and M is at least one element selected from the groupconsisting of As, Sb, Bi, S, Si, Ge, Sn, Pb, Al, Ga, In, Tl, Zn, Cd, Au,Ag, Cu, Ni, Pd, Rh, Cr, Mo, W and Ta, which is formed on a substrate,(2) irradiating a recording beam to said information recording film tocause a phase transition of said information recording film, said phasetransition being a transition between the amorphous and crystallinephases, and (3) detecting the condition of said phase transition of saidinformation recording film.
 2. A method as defined in claim 1, whereinthe recording beam is a laser beam.
 3. A method as defined in claim 1,wherein the elements expressed by M in said general formula include atleast Sn.
 4. A method as defined in claim 1, wherein the elementsexpressed by M in said general formula include at least In.
 5. A methodas defined in claim 1, wherein the elements expressed by M in saidgeneral formula include at least Sb.
 6. A method as defined in claim 1,wherein M is a combination of two elements, said combination of twoelements being selected from the group consisting of In and Sb, Sn andGe, Pb and Sn, Sn and Bi, Sn and S, In and Pb, In and Bi, Sb and Bi, Sband S, Sb and Pb, Sb and Sn, Sb and Ge, As and Sn, and As and Sb.
 7. Amethod as defined in claim 6, wherein M is a combination of twoelements, said combination of two elements being selected from the groupconsisting of Sn and Ge, Pb and Sn, Sn and Bi, Sn and S, Sb and Sn andAs and Sn.